Abstract
Compost recycling is one of the methods of watershed management to reduce pollutant load flowing to the river system. An evaluation system for compost recycling scenarios was developed for watershed water quality management in Lake Kasumigaura basin, Japan. The basin was divided into six regions, and the nitrogen effluent loads of each region were computed from the GIS database constructed from the statistical data of each city. Outflow loads to Lake Kasumigaura were calculated with a water tank model classified by land use. Four scenarios concerning compost recycling were developed, and the outflow loads to Lake Kasumigaura were predicted over 10 years. As a result, the nitrogen load reduction ratio was about 10 to 40% according to the characteristics of scenarios or regions; in the scenario of compost recycling within the entire watershed, the nitrogen load was reduced in the region of high livestock waste load, and the nitrogen load increased in the region that received compost.
